Major Depression is one of the most common mental health disorders in adolescence and is associated with significant impairments in development and functioning. This project will rigorously test the Adolescent Collaborative Care Treatment intervention, a health services intervention designed to improve management for depressive disorders among adolescents, via a randomized controlled trial comparing the intervention to usual care. Key components of the trial include enhanced education for youth and parents, youth involvement in choice of evidence-based treatments, care management by an allied health professional with regular supervision by a mental health specialist and pediatrician, and stepped care to advance treatment when youth are not improving. Additional features have been added to engage adolescents and parents including a moderated message board for youth to share with and learn from one another, formalized involvement of the parent, and availability of the care manager during after school hours. Our findings will provide key information on the effectiveness of a developmentally-sensitive adapted collaborative care intervention for the treatment of adolescent depression. PUBLIC HEALTH RELEVANCE: The goal of the current adolescent depression intervention is to markedly improve the percentage of adolescents who are accurately diagnosed and effectively treated for depression. Fewer than 50% of youth with depression receive treatment. Most adolescents visit a primary care doctor at least once a year: improving the detection and treatment of depression in this setting could markedly improve depression outcomes in teenagers and decrease risk of suicide.